Ind. Eng. Chem. Prod. Res. Dev. 1980, 79, 551-556
The stability tests show that catalysts with 0.8-0.9% chlorine are less affected during deactivation; their rate of coke formation is smaller. For each parameter the slopes of decay and drop during deactivation have the same sign and they are nearly proportional. Acknowledgment The authors are grateful to R. Lazzaroni, A. Cinquegrani, and G. Imbert for their help in the experimental work and to S. Garcia and A. Bezombe for the chlorine determinations. Literature Cited Anderson, P. C.. Sharkey, J. M., Waish, R. P., J . Inst. Pet., 58, 63 (1972). Apesteguia C., Petunchi, J., Rincbn, E., First Latin American Congress on Petrochemistry, S.C. de Bariloche, Argentina, 1976. Benke, A. H., Ph. D. Thesis, University of California, Berkeley, 1976. Benson, J., Boudart, M., J. Catal., 4, 704 (1965). Burfieid, D. R., Gan, G. H., Smithers, R. H., J. Appl. Chem. Biotechnol., 28, 23 (1976). Carter, J. L., Lucchesi, P. J., Corneii, P., Yates, D. J. C., Sinfelt, J. H., J. Phys. Chem., 69, 3070 (1965).
55 1
Castro, A. A., Sceiza, 0. A,, Benvenuto, E. R., Baronetti, G. T., Parera, J. M., 6th Iberoamerican Symposium on Catalysis, Rio de Janeiro, Brazil, Paper No. 55, 1978. Cipetta, F. G., PefrolChem. Eng. 33, C-19 (1961). Figoii de Parera, N. S., Sad, M. R., Rausei, D. N., Rev. Fac. Ing. Quim., 42, 31 (1977). Gates, B. C., Katzer, J. R., Schult, G. C. A,, "Chemistry of Catawc Processes", p 190, McGraw-Hili, New York, 1979a. Gates, B. C., Katzer, J. R., Schult, G. C. A,, "Chemistry of Cataty-tic Processes", p 287, McGraw-Hili, New York, 1979b. Haensei, V., Donaldson, G. R., Ind. Eng. Chem., 43, 2102 (1951). Hail, W. K., Lutinski, F. E., J. Catal.. 2, 518 (1963). Hettinger, W. P., Keith, C. D., Wings, J. L., Teter, J. W., Ind. Eng. Chem., 47, 719 (1955). Nevison, J. A., Obaditch, C. J., Daison, M. H., Hydrocarbon Process., 53(6), 111 (1974). Nowak. E. J., J. Phys. Chem., 73, 3790 (1969). Sad, M. R.. Rausei, D. N., Jabionski, E. L., Figoii de Parera, N. S . , Rev. Fac. Ing. Quim., 42, 45 (1977). Sinfelt, J. H., Hurwitz, H., Rohrer, J. C., J . Catal., 1, 461 (1962). Svajgi, O., Int. Cbern. Eng., 12, 55 (1972). Tanaka, M., Ogasawa, S . , J. Catal., 16, 157 (1970). Van Keuien, G. J. M., "hoceedlngs, Sixth International Congress on Catalysis", London, 1976, p 1051, The Chemical Society, London, 1977. Waish, R. P., Mortimer, J. V., Hydrocarbon Process., 50, 153 (1971).
Received for review November 19, 1979 Accepted March 24, 1980
Zinc-Promoted Raney Copper Catalysts for Methanol Synthesis Warwlck L. Marsden, Mark S. Wainwright,' and Jan B. Frledrlch School of Chemical Technology, The University of New South Wales, Kensington, New South Wales, Australia, 2033
Copper-based catalysts have been prepared by the Raney method and have been demonstrated to have high activii for the synthesis of both methanol and methanoVdimethy1ether mixtures. A range of alloys containing 50 wt % aluminum, with between 0 and 50 wt % copper, and the balance zinc was prepared and extracted with a 20 wt % NaOH solution. Hybogenation experiments were performed on the resultant catalysts using CO/H, and CO/C02/H2 mixtures at temperatures from 225 to 290 OC, pressures from 2750 to 6900 kPa, and linear hourly space times between 0.001 and 0.5 h. The optimum activity was found in catalysts produced from alloys containing 50 wt % aluminum, 33-43 wt % copper and 7-17 wt % zinc. Raney catalysts of optimum composition were found to have activities for methanol production comparable to that of a commercial copper-based methanol synthesis catalyst. The Raney catalysts produced small amounts of byproduct dimethyl ether which is thought to be formed by dehydration on residual, high-activity alumina produced by the extraction procedure.
Introduction Although the first patent for methanol synthesis on copper-based catalysts was filed as early as 1921by Patart (Haynes, 1948),these catalysts were not used commercially for almost half a century due to the low thermal stability of copper and its susceptibility to sulfur poisoning. Interest in copper-based catalysts was revived when IC1 developed a process for producing synthesis gas relatively free of impurities by steam reforming of naphtha (Humphreys et al., 1974). This led to the development by IC1 in the late 1960's of the modern low pressure, low temperature methanol synthesis process. Parallel to the development by IC1 was the development of further gas purification processes, such as the Lurgi Rectisol process (Supp, 1973), so that now synthesis gas essentially free of sulfur can be produced from coal as well as natural gas and crude oil. The modern IC1 methanol process was initially based on ternary catalysts containing copper oxide (which was reduced in situ), zinc oxide, and chromic oxide (Davies and 0196-4321/8011219-0551$01 .OO/O
Snowdon, 1967),and the conditions used were in the order of 250 to 270 "C and 5000 to 10000 kPa. Further research has shown that if alumina is used in place of chromic oxide longer catalyst life results, and so most low pressure catalysts now contain alumina rather than chromic oxide as the third component (Casey and Chapman, 1974). These catalysts are produced by coprecipitation of soluble zinc and copper salts (usually the nitrates) with an alkali carbonate solution. The resulting mixture of carbonates is heated to form a mixture of oxides which are then mixed with aluminum oxide. Further improvements in methanol production will be made by the development of catalysts that have higher intrinsic activity, selectivity, thermal stability, and resistance to poisoning. This paper describes the preparation of a novel range of zinc-promoted Raney copper catalysts which have been shown to have high activity and stability. Experimental Section Figure 1 shows a flow diagram of the procedures used in catalyst preparation and characterization. The com0 1980 American Chemical Society
552
Ind. Eng. Chem. Prod. Res. Dev., Vol. 19, No. 4, 1980
Table I. Catalyst and Alloy F'ropertiesa cat. properties alloy compositions, wt % cat. 1 2 3 4 5 6 7 8 9 10 11 12 Indd
nominal A1 Cu Zn
50 50 50 50 50 50 50 50 50 50 50 50 -f
50 45 33.3 16.7 0 41 42 42 40 40 40 40
-
cat. compositions, wt %
analysis Cu Zn A1
0 5 16.7 33.3 50 9 8 8 10 10 10 10
47.3 47.3 45.6 47.9 49.1 50.1 47.5
52.7 48.2 37.6 16.1 0 38.9 44.6
0 4.4 16.8 36.0 50.9
48.1 48.1 48.1 48.1
42.1 42.1 42.1 42.1
9.8 9.8 9.8 9.8
11.0 7.9
-
-
Al
before use Cu Zn othere
2.9 4.6
94.9 89.1
-f
-
11.7 3.8 3.3 6.2 4.2 5.6 9.7 4.7
-
64.7 79.9 86.3 70.2 79.8 75.4 66.8 46.5
Al
2.2 6.2 10.0 13.0 22.0 10.1 13.5 12.4 4.7 11.7 2.9 7.6 8.5 15.2 6.2 4.3 5.3 11.7 7.3 11.8 5.4 4.7 10.4 18.9 27.2 21.7 -
0 2.5
2,2 3.8
-
-
after use Zn Cu
0 87.8 2.9 88.3 61.8 16.7 27.5 45.1 0 51.8 62.3 9.1 70.1 8.9 5.2 79.9 7.5 75.4 66.8 20.3
surface bulk area, mz g-' density othere b c gcm-'
10.0 20.8 2.6 42.8 11.5 14.4 26.2 35.3 16.2 51.6 39.4 14.7 50.9 11.2 55.5 11.8 63.5 2.4 50.1 53.3
22.7 37.7 54.0 53.0 42.8 51.8 64.4 49.0 39.2 65.8 28.2 23.3 30.7
1.10 1.25 1.42 1.44 1.23 1.29 1.14 1.03 1.31 1.26 1.10 1.23 1.11
Particle size of catalysts: 35-45 mesh. Before methanol synthesis. After methanol synthesis. United Catalysts Inc. C79-4, low temperature methanol catalyst. e Mainly oxygen with some traces of sodium. f Dashes indicate not measured. A A S S.AA GC
-
Atomic Absorption Spec1roscopy S u r f a c e Area Analysis Chrornotogroph
- Gas
1 Crushing
Extraction
Washing
U
Figure 1. Flow diagram for the preparation and characterization of catalysts for the production of methanol.
plexity of a program to fully examine this sytem of catalysts can be understood by examining each stage in the process. In this study we have investigated alloy composition, extraction temperature, the method of caustic addition, as well as the variables for methanol synthesis; these variables are temperature, pressure, feed composition, and space time. Catalyst Preparation. All of the h e y catalysts were prepared from eight alloys containing nominally 50 wt % aluminum and varying amounts of copper and zinc. Alloys were prepared from high purity metals (A1 > 99.9%, Zn > 99.8%, Cu > 99.5%). The compositions of the alloys are given in Table I. The 50 wt 9% AI was used since it corresponds to the composition CuA12in the copper-aluminum alloy used to produce Raney copper. CuAlz is known to be the leachable phase (Nadirov et al., 1977). The alloys were prepared in carbon crucibles heated in an induction furnace. Alloys samples of between 200 and 400 g were prepared in each batch. Copper, having the highest melting point, was melted first and then aluminum was added. After vigorous stirring with a carbon rod the melt was cooled to below the boiling point of zinc before that metal was added with stirring. The melt was then rapidly quenched in cold water. The resulting alloy samples were crushed in a jaw crusher and screened. The aluminum-zinc alloy was cooled in liquid nitrogen in order to make it sufficiently brittle to crush. Catalysts were prepared from the alloys by a method similar to that adopted in a previous study using Raney Ni alloys (Free1 et al., 1969). The catalyst was extracted over a 2-h period. During the first hour caustic soda (40%
w/v) was added to a suspension of the alloy in water until the final solution was 20% w/v. After the extraction the catalyst was washed with distilled water at 25 "C, first by decantation and finally by water flow until the pH of the wash water was 7. The catalyst was then screened under water to remove any particles passing through a 45-mesh screen. The method of caustic addition and temperature of extraction are discussed later and have been summarized in Table 111. A sample of C79-4 low-temperature methanol synthesis catalyst was obtained in the form of 3/ls-in. pellets from United Catalysb Inc., Kentucky. This catalyst is an improved version of the copper-based catalyst described in the patent by Casey and Chapman (1974). The aproximate composition and surface areas are given in Table I. Catalyst Characterization. Acid digests of the alloys and catalysts were analyzed for aluminum, zinc, and copper content by atomic absorption spectroscopy. Compositions of alloys and catalysts are given in Table I. The surface areas of catalysts were measured by nitrogen adsorption at -196 "C using a Micromeritics 2200 High Speed surface area analyzer. The specific surface areas are given in Table I. Reaction Apparatus and Procedure. Experiments to measure catalyst activity and selectivity were performed in conventional flow reactors. A tubular reactor, constructed from 12.7 mm 0.d. seamless copper tubing, was used in the experiments performed with catalysts 1 through 6. All further experiments were conducted in a U-tube reactor constructed from 9.7 mm 0.d. seamless copper tubing. Experiments showed that the empty reactors had no catalytic activity. The reactors were immersed in vigorously stirred, molten salt baths in order to obtain quasiisothermal reaction conditions. The temperature of the bath was controlled to i 0 . 5 "C using a PID controller. Premixed gases containing CO/Hz and CO/C02/H2 (Commonwealth Industrial Gases Ltd.) were fed from high-pressure cylinders to the reactor via a needle valve. The exact compositions of the feed gases were determined by gas chromatography and confirmed using an Anarad Model AR-6000R CO/C02 infrared gas analyzer. The pressure in the reactor was controlled using a back-pressure regulator and was measured by a Bourdon gauge. The flow rate of the exit gases was measured using a wet gas meter. The composition of the reador effluent was determined by gas chromatography. A Gowmac Model 552 gas chro-
Ind. Eng. Chem. Prod. Res. Dev., Vol. 19, No. 4, 1980 553
08-
h l
-
z 0 10
06-
-
CL
y04z U 0
02-
CONVERSION ( C O )
A L L O Y COMPOSITION ( w t % Z n )
Figure 3. Selectivities for the hydrogenation of carbon monoxide over catalyst 1 (0% zinc in initial alloy).
Figure 2. Conversion of carbon monoxide vs. nominal zinc content in the original alloys for various space times.
1
matograph equipped with a thermal conductivity detector was employed, A Porapak T column (3 m X 6.3 mm 0.d. aluminum), operated isothermally at 150 "C, gave excellent separation of CO, COz, dimethyl ether, water, and methanol. Hydrogen was employed as carrier gas and hence was not detected in the reactor effluent. Peak areas were measured using a Spectra-Physics Minigrator electronic integrator. The thermal conductivity detector was calibrated daily using a gravimetric standard mixture containing CO, COz and dimethyl ether in hydrogen (Commonwealth Industrial Gases Ltd.). The range of experimental conditions employed was chosen to represent those in industrial reactors employing low-temperature methanol synthesis catalysts. In most experiments the hydrogenation reactions were conducted at 275 "C and 5500 kPa. Other conditions employed are mentioned later in the paper. Results Comparison of catalysts properties is made on the basis of the nominal compositions of the starting alloys. The various properties are discussed under separate heatings below. Catalyst properties are summarized in Table I. Specific Surface Areas of Catalysts. From the results in Table I it can be seen that the specific surface area increased with zinc content of the alloys up to 17 wt % zinc. It should be noted that the extraction procedures adopted in this work were not isothermal and could lead to variations in surface areas of catalysts. However, further work in the method of extracting alloys in the optimal composition range (7 to 17% Zn) is necessary to prepare catalysts of maximum surface area. Activity of Catalysts. The overall activity of a catalyst was measured by its ability to convert carbon monoxide to products including methanol, dimethyl ether, and carbon dioxide. Figure 2 shows the conversion of carbon monoxide plotted against alloy composition for catalysts 1 through 6 at various space times. The curves show an apparent maximum in activity for catalysts prepared from an alloy containing 50 wt % aluminum with 33-43 wt % copper and 7-17 wt % zinc. Selectivity of Catalysts. The results for the hydrogenation of carbon monoxide over catalysts 1 through 6 showed high selectivity to methanol at low space times for catalysts 1, 2, 3, and 6 which contain low zinc levels. However, this selectivity decreased with increasing zinc
5500 * P o
?. i
275'C
B Me01 A DYE
Figure 4. Selectivities for the hydrogenation of carbon monoxide over catalyst 2 (5% zinc in initial alloy).
75
0
1
3 P = 5500 kPo MeOH T;275*C ADME to'; 17 ~ r n a l c v . 8 C 0 2
CATALYS'
2
L
6
10
CONVERSION ( C O )
Figure 5. Selectivities for the hydrogenation of carbon monoxide over catalyst 3 (17% zinc in initial alloy).
content for catalysts 4 and 5. The selectivities of catalysts 1, 2, and 3 are plotted against conversion of carbon monoxide in Figures 3,4, and 5, respectively. In these plots the selectivity to methanol is seen to drop sharply at low conversions for catalyst 1
554
Ind. Eng. Chem. Prod. Res. Dev., Vol. 19, No. 4, 1980
Table 11. Rates of Methanol Production over Zinc-Promoted Raney Copper Catalysts and an Industrial Methanol Synthesis Catalyst a ~
feed compn (bal H,) cat.
CO, mol %
CO,, mol %
LHST, h
3 3 3 3 3 3 6 6 industrial industrial industrial industrial industrial
17.8 17.8 17.8 12.9 12.9 12.9 15.9 15.9 14.9 14.9 20.8 20.8 20.8
0 0 0 2.01 2.01 2.01 2.33 2.33 2.15 2.15 1.77 1.77 1.77
0.001 0.004 0.010 0.001 0.004 0.010 0.001 0.004 0.001 0.004 0.001 0.004 0.010
~~
~
rate of methanol synthesis, selectivity ratio, cm3 CH,OH/ SCH,OCH,/ h cm3 cat. SCH,OH 0.58 0.043 0.71 0.031 0.54 0.052 0.006 1.77 0.017 1.16 0.024 0.56 1.15 0.043 0.08 0.67 0 1.20 0.81 2.51 0.77 0.60
0 0 0
0.001
Conditions of reaction: pressure, 5500 kPa; temperature, 275 "C. Table 111. Summary of Extraction Conditions cat.
method of NaOH addition
1-5 6 7 8 9 10
13 equal additions a t 5-min intervals 13 additions of increasing volumes continuous addition 13 equal additions 13 equal additions 13 equal additions continuous addition continuous addition
11
12
and less sharply for catalyst 2. In the case of catalyst 3 the decrease in selectivity with conversion is very small. A similar trend was observed in the hydrogenation of a mixture of carbon monoxide and carbon dioxide. The selectivity to dimethyl ether is the mirror image of the methanol selectivity curves in Figures 3,4, and 5. This indicates that dimethyl ether is formed from methanol by a dehydration reaction 2CH3OH = CH30CH3 + H20 (1) When a mixture of carbon monoxide and carbon dioxide was hydrogenated the selectivity to dimethyl ether was reduced. The selectivity to carbon dioxide decreased with increased zinc content for catalysts 1 to 3. This indicates that the carbon dioxide is produced by the shift reaction CO + H20 = C02 H2 (2) through water produced by the dehydration reaction (eq 1). Rate of Methanol Production. A comparison of methanol production rates between the zinc-promoted Raney copper catalysts in the optimal composition range and those of the industrial catalyst is made in Table 11. It can be seen that catalysts 3 and 6 have activities, (expressed as cm3 of liquid methanol produced per cm3 of catalyst) comparable to the industrial catalyst under similar reaction conditions. Extraction Procedures. The extraction of aluminum alloys to produce Raney catalysts is a complex procedure with many variables including caustic concentration, rate of caustic addition, and temperature being among the most important. The process is even more complex when a second leachable component such as zinc in included in the alloy system. Preliminary experiments to determine the effects of temperature and caustic addition were made with two alloys having composition in the optimum range. As with the extraction of alloys 1to 6, caustic was added
+
temp of max temp extraction, "C differential, "C 25 25 45 60 25 50 50 30
up t o 40 13-18 7 12 23 18 6 6
designation of extraction harsh moderate mild moderate harsh very harsh mild very mild
Table IV. Influence of Extraction Conditions on Activity and Selectivity ( a ) feed compn
cat. 9 10 11
12 7 8 9 a
(bal H2) CO, CO,, mol % mol % 1.77 20.8 20.8 1.77 20.8 1.77 20.8 1.77 0 21.7 0 21.7 0 21.7
selectivity converratio, sionof SCH,OCH,/ CO SCH.OH 0.35 0.042 0.25 0.131 0.01 1.40 neg. 7.13 0.02 1.38 0.15 0.390 0.21 0.148
Space time: 0.01 h.
in a 200% excess of that required for complete leaching of the aluminum present. The extraction procedures and temperatures of extraction are summarized in Table 111. The temperature of extraction is divided into two parts. The first refers to the temperature of the water bath in which the extraction vessel was placed. The other refers to the temperature rise within the extraction mixture. From Table I it can be seen that no clear relationship exists between the conditions of extraction and the surface area of the catalyst prior to use in the reactor. The conditions of extraction have a marked effect on catalyst activity and selectivity as can be seen in Table IV. Harsh conditions of extraction produce catalysts with high activity and selectivity for methanol production (catalysts 8, 9, and lo), whereas catalysts produced by milder extraction of the same alloys had low activities and high selectivities to dimethyl ether formation. Effect of Temperature and Pressure. Initial experiments were conducted on catalyst 3 to determine the influence of temperature and pressure on the hydrogenation of carbon monoxide. The catalyst showed little activity below 240 "C. The influence of total pressure be-
Ind. Eng. Chem. Prod. Res. Dev., Vol. 19, No. 4, 1980 555 1-6 c o o : 18rnolP/* *f: 82mole% P ; 5500 kPo 1 = 273 'C LHST i 0.001 h
CATALYSTS
.
30.
Role per " n i l m o s s o f c d a l p t .Id Igmoi g c a l l h-' I
.
Rote p e ? u n l l v o l u m e 0 1 c o l o l y r l
2 20 W
Z
0 Q
k! 10
.[\ .
~
I
.dk~
.
Rate per u n i t s u r f a c e
o f cataiyst
~ 0110
l o 5 igmol m2 6' I
~
I
dimethyl ether is doubtless formed by the dehydration of methanol on an active form of alumina. Until recently (Casey and Chapman, 1974) alumina has been considered an undesirable component in methanol synthesis catalysts because it does cause the formation of byproduct dimethyl ether. However, modern formulations include an inactive form of alumina to provide thermal stability in the catalyst. In this study significant yields of dimethyl ether were only produced at high conversions to methanol on catalysts of near optimum composition. This indicates that the amount of active alumina is small and/or the rate of the dehydration reaction is slow compared with methanol synthesis. It was also found that dimethyl ether formation was reduced by operating at higher pressures. Dimethyl ether is an undesirable byproduct in methanol synthesis when methanol is desired as a solvent or chemical feedstock. However, it is an intermediate in the production of gasoline from methanol via the Mobil process (Voltz and Wise, 1976). In fact in their fixed bed laboratory process a preliminary bed of dehydration catalyst (presumably y-A1203)is used to form an equilibrium dimethyl ether/ methanol mixture to feed to the fixed bed of ZSM-5 catalyst to produce gasoline. A recent Mobil patent (Zahner, 1977) claims the use of a fixed bed of mixed methanol synthesis catalyst and dehydration catalyst to produce a mixture of methanol and dimethyl ether from synthesis gas. An earlier patent (Chang and Silvestri, 1975) claims the use of a 1:l mixture of a copper (methanol synthesis) catalyst and alumina (acidic dehydration) catalyst to produce dimethyl ether from synthesis gas. The catalysts produced in this study are capable of producing both methanol and dimethyl ether in varying quantities depending on the conditions of reaction (contact time and pressure) and method of extracting the alloy. From the results presented in Tables I11 and IV it is apparent that the conditions of extraction are most important in determining catalyst activity and selectivity. Mild extraction conditions produce catalysts of low activity and high selectivity to dimethyl ether formation. This is most likely due to the formation of larger amounts of surface alumina under these conditions. This alumina is active for dehydration but totally inactive for methanol synthesis. The milder conditions probably result in a higher surface area of active alumina relative to copper and zinc oxide, while the more vigorous conditions bring about a removal of much of this residual alumina. Of considerable importance in the development of catalysts for methanol synthesis is catalyst stability. Catalysts were employed over a period of several weeks with no apparent loss in activity when CO/C02/H2mixtures were employed. However, a linear decay in activity was noted when no C02was present in the synthesis gas. Typically, one catalyst of near optimum composition exhibited a linear loss in activity to 80% of the original activity after 260 h of continuous operation at 275 "C. The influence of C02 in the synthesis gas for the h e y catalysts was similar to that for the industrial catalyst. In general, the presence of as little as 2% C02gave a threefold increase in activity, for synthesis gases containing between 12 and 25% CO. The COPwas not consumed in the reaction under the conditions employed. In the case of synthesis gas containing no C02it was noted that at high space times water produced in the formation of dimethyl ether caused the shift of CO to C02 and increased the catalyst activity. These findings are in accordance with those of an extensive investigation of methanol synthesis catalysts (Herman et al., 1979) in which a solution of CUI in ZnO is concluded to be the active catalyst component.
556
Id.Eng. Chem. Prod. Res. Dev. 1980, 19, 556-563
The results of the current study support the view that the principal role of COzis to maintain the catalyst in an active state rather than to take place in a direct hydrogenation to methanol. Conclusions This study has demonstrated that novel catalysts of the Raney type, produced by the caustic extraction of aluminum-copper-zinc alloys shows high activity and selectivity for methanol synthesis. The main factors which affect the ability of these catalysts to produce methanol are the composition of the starting alloys and the extraction procedures used to leach the aluminum and some of the zinc from the alloy. While the composition of the final catalyst was found to be a function of both the initial alloy compositon and the extraction conditions, an alloy composition range for optimal methanol synthesis catalysts was found to be 33-43 w t 7% copper, 7-17 w t % zinc and 50% aluminum. Conditions of extraction were found to have marked influence on selectivity. In general, catalysts prepared under more severe the conditions exhibit higher selectivity and activity for methanol synthesis. I t is apparent that considerably more research is required into these catalysts, first intothe quite complex area of alloy extraction and secondly into their industrial applicability with regard to poisoning and thermal stability,
two properties which have caused problems in other copper-based methanol synthesis catalysts (Dewing and Davis, 1975). Literature Cited Casev. T. D.: ChaDman, G. M. (to Cataksts and Chemicals. Inc.), US. Patent ' 3 790 505,F i b 5. 1974. Chang, C. D.; Sihrestrl. A. J. (to Mobile Oil Corporation), US. Patent 3 894 102, lune 1975. I-'.-. Davles, P.; Snowdon, F. E. (to Imperial Chemical Industries Ltd.), U S . Patent 3 326 956,June 20, 1967. Dewlng, J.; Davis, D. S. Adw. Catai. 1975, 24, 221. Freel, J.; Pleters, W. J. M.; Anderson, R. B. J. Catal. 1969, 14. 247. Haynes, W. "American Chemlcal Industry-A History, Vol. I V 1923-29";Von Nostrand Co.;Amsterdam, 1948;p 169. Herman, R. G.; Kller. K.; Simmons, G. W.; Finn, 8. P.; Bulko, J. B.; Kobylinski, T. P. 1979, J. Catai. 1979, 56. 407. Humphreys, 0.C.; Ashman, D. J.; Harris, N. Chem. €con. Eng. Rev. 1974. 6, 26. Nadlrov, N. K.; Ashirov, A. M.: Savel'ev, A. F.; Zhusupova. A. 2.flz. Khim. 1977, 51, 1422. Schermuiy, 0.;Luft, G. Chem. Ing. Techn. 1977, 49, 11. Supp, E., Chem. Tech., 3,430 (1973). Vokz. S. E.; Wise, J. J. "Development Studies on Conversion of Methanol and Related Oxygenates to Gasoline", 1978,Final Report, ERDA ERDA E(40-
18b 1773. Zahner, J. C. (to Mob11 Oil Corp.), U.S. Patent 4 011 275,Mar 8. 1977.
Received for reuieu January 16, 1980 Accepted June 26, 1980 Support was provided under the National Energy Research, Development and Demonstration Program administered by the Commonwealth Department of National Development.
Steam Cracking of Hydrocarbons. 3. Straight-Run Naphtha Martin Bajus and VBclav Veselg Department of Chemistry and Technology of Petroleum, Slovak Technical University, Bratislava, Czechoslovakla
Plet A. Leclercq and Jacques A. Rljks' Laboratory of Instrumental Analysis, Elndhoven University of Technology, Eindhoven, The Netherlands
Steam cracking of straight-run naphtha from Romashkino crude oil was investigated in quartz and stainless steel reactors with a relatively large ratio of Inner surface to volume. The experiments were performed at atmospheric pressure at 780-800 OC for starting ratios of steam to naphtha between 0.5 and 1.0, with residence times of 0.1-0.4 s. The influence of the reactor material, the temperature, the ratio of steam to hydrocarbon, the residence tlme, and the presence of sulfur compounds is discussed in terms of coke formation and yields of various reaction products. The reaction products were analyzed by gas chromatography, using packed columns for the analysis of the gaseous products and capillary columns for the liquid products. About 200 compounds were identified in the liquid mixture. Reference standard hydrocarbons, published retention data, and mass spectrometry were used for the identifi&tiOn.
Introduction In the pyrolysis of individual hydrocarbons and petroleum fractions to desired olefins, not only primary reactions but also secondary reactions occur. Many products of splitting, dehydrogenation, hydrogenation, and condensation reactions are formed. The composition of the product mixture is influenced by the reaction conditions. Important factors are also the type of reactor, the properties of the construction material, the ratio of inner surface to volume, and the activation or passivation of the inner surface of the reactor by chemical compounds. The pyrolysis of ethane (Dunkleman and Albright, 1976a;
Brown and Albright, 1976),propane (Brown and Albright, 1976; Crynes and Albright, 1969; Tamai and Nishiyama, 1970; Dunkleman and Albright, 1976b),butanes (Hurd and Pilgrim, 1933), heptane (Melikadze et al., 1975; Bajus et al., 1979a),methylcyclohexane (Bajus et al., 1979b),ethene (Brown and Albright, 1976; Hurd and Eilers, 1934), propene (Hurd and Eilers, 1934; Ghaley and Crynes, 1976), methylpropene and its dimers, and 2-pentene (Hurd and Eilers, 1934) has been investigated. Nonmetallic materials (glass, quartz, porcelain), metals (iron, nickel, gold, silver, cobalt, titanium), alloys (monel, ascoloy, incoloy 800),and stainless steel of different compositions were used as re-
0196-4 2118011219-0556$01.0010 0 1980 American Chemical Society
